> The app knowing I took a screenshot feels adjacent to me to a keylogger.

To my knowledge, this is a misunderstanding. The app does not know that you are taking a screenshot, rather iOS knows you are taking a screenshot (as it must) and is excluding an element on display that has been designated by the developer as sensitive information. This is the same technology that prevents you from accidentally screenshotting your password manager; the developer has simply performed a nifty trick to display a small icon behind where the “follow” button would otherwise be displayed.

There are plenty of instances where this sort of thing can be annoying, such as when you try to screenshot a streaming service app and DRM enforcement leaves you with a blank screenshot, but IMO this particular instance is actually very tasteful; seeing “follow” on every screenshotted post is just useless noise, but a small unobtrusive platform icon is a useful reminder that the post came from Bluesky and not another very visually similar service like X(cancel) or Mastodon.

> The app knowing I took a screenshot feels adjacent to me to a keylogger.

That is what this article is about and why you should read it before commenting. The whole point is that it doesn't need to know you're taking screenshots. That's why it's a clever trick.

but you didn't read the part where the mechanism is explained? it doesn't do anything like capturing information. it just marks a button "sensitive" causing it to be hidden in a screenshot, thus revealing an icon that was put there underneath the button.

Did you read the article? Bluesky doesn't know you're taking a screenshot, iOS just hides the follow button in the screenshot (consequently making the Bluesky logo visible).